1. Field of the Invention
This invention relates to improvements in an oil pan for an automotive vehicle, and more particularly to the oil pan with which splashed oil is effectively returned into a sump section.
2. Description of the Prior Art
It is well known that an internal combustion engine is provided with an oil pan with which lubrication oil dropped in the oil pan is collected in a sump of the oil pan to be fed to various sections of the engine by an oil pump. In order to effectively return the lubrication oil into the sump, it has been proposed that an oil pan has a plurality of guide ribs on a shallow bottom section of the oil pan as shown in the FIG. 7 of the present application. Such an arrangement is disclosed, for example, in Japanese Patent Publication 53-16048.
As shown in FIG. 7, an oil pan 51 includes a sump 52 which is disposed under a cylinder block and along the axis of a crankshaft. A shallow bottom section 53 is disposed under the cylinder block and defines a space which is communicated with the sump section 52. An oil strainer (not shown) is disposed in the sump section 52. A generally straight rib 54 is formed at the upper surface on one side of the shallow bottom section 53 which side is located downstream of the oil flow caused by the rotation of the crankshaft. The straight rib 54 extends generally in the longitudinal direction of the engine. A plurality of arcuate ribs 55 are formed at the upper surface on the side of the shallow bottom section 53. Lubrication oil in the shallow bottom section 53 is forced in the direction indicated by arrows A under the rotation of the crankshaft. This causes lubrication oil to be rapidly returned from the shallow bottom section 52 into the sump section 52. The shallow bottom section 53 is located considerably near the crankshaft since modern engines have become formed smaller.
However, with this conventional arrangement, lubrication oil guided by the ribs 55 flows into the sump section 52 through a flat section 56 which is formed between the rib 54 and the end 55a of the each rib 55. Therefore, the oil tends to be splashed by the crankshaft and connecting rods. This causes the problems that the oil amount lacks in the sump section 52, and therefore air is sucked into an oil flowing circuits through the oil strainer. Thus, a large amount of air bubble is mixed with the oil.